Earth-boring rotary drill bits are commonly used for drilling boreholes or wells in earth formations. One type of rotary drill bit is the fixed-cutting element bit (often referred to as a “drag” bit), which typically includes a plurality of cutting elements secured to a face and gage regions of a bit body. Generally, the cutting elements of a fixed-cutting element-type drill bit have either a disk shape or, in some instances, a more elongated, substantially cylindrical shape. A cutting surface comprising a hard, superabrasive material, such as mutually bound particles of polycrystalline diamond forming a so-called “diamond table,” may be provided on a substantially circular end surface of a substrate of each cutting element. Such cutting elements are often referred to as “polycrystalline diamond compact” (PDC) cutting elements. Typically, the PDC cutting elements are fabricated separately from the bit body and secured within pockets formed in an outer surface of the bit body. A bonding material such as an adhesive or, more typically, a braze alloy may be used to secure the cutting elements to the bit body.
The bit body of an earth-boring rotary drill bit may be secured to a hardened steel shank having American Petroleum Institute (API) standard threads for connecting the drill bit to a drill string. The drill string includes tubular pipe and equipment segments coupled end to end between the drill bit and other drilling equipment at the surface. Equipment such as a rotary table or top drive may be used for rotating the drill string and the drill bit within the borehole. Alternatively, the shank of the drill bit may be coupled directly to the drive shaft of a down-hole motor, which then may be used to rotate the drill bit.
Referring to FIG. 1, a conventional fixed-cutting element rotary drill bit 10 includes a bit body 12 that has generally radially projecting and longitudinally extending wings or blades 14, which are separated by junk slots 16. A plurality of PDC cutting elements 18 are provided on the face 20 of the blades 14 extending over face 20 of the bit body 12. The face 20 of the bit body 12 includes the surfaces of the blades 14 that are configured to engage the formation being drilled, as well as the exterior surfaces of the bit body 12 within the channels and junk slots 16. The plurality of PDC cutting elements 18 may also be provided along each of the blades 14 within pockets 22 formed in the blades 14, and may be supported from behind by buttresses 24, which may be integrally formed with the bit body 12.
The drill bit 10 may further include an API threaded connection portion 30 for attaching the drill bit 10 to a drill string (not shown). Furthermore, a longitudinal bore (not shown) extends longitudinally through at least a portion of the bit body 12, and internal fluid passageways (not shown) provide fluid communication between the longitudinal bore and nozzles 32 provided at the face 20 of the bit body 12 and opening onto the channels leading to junk slots 16.
During drilling operations, the drill bit 10 is positioned at the bottom of a wellbore and rotated while drilling fluid is pumped through the longitudinal bore, the internal fluid passageways, and the nozzles 32 to the face 20 of the bit body 12. As the drill bit 10 is rotated, the PDC cutting elements 18 scrape across and shear away the underlying earth formation. The formation cuttings mix with and are suspended within the drilling fluid and pass through the junk slots 16 and up through an annular space between the wall of the borehole and an outer surface of the drill string to the surface of the earth formation.